The present invention relates to an improved form of steam iron, having a water tank from which water can be supplied to a steam generating chamber to be rapidly vaporized therein with the steam thus generated being ejected through apertures in the soleplate of the iron onto a material which is being ironed.
More specifically, the invention is directed towards an improved steam iron of this type, which enables convenient selection of each of a plurality of operating modes. These are, respectively, an operation mode in which water is continuously admitted to the steam generating chamber at a limited fixed flow rate, for continuous steam generation, a mode of operation in which a momentary flow of a large quantity of water into the steam generating chamber is executed to produce a surge of steam from the iron, and a mode of operation in which no steam is generated.
Generally, a steam iron has the steam generating chamber formed in the soleplate, which is heated by an electric heating element, and water is supplied to the steam generating chamber from the water tank through a nozzle having a small-diameter aperture formed therein. A valve mechanism is normally incorporated, which is actuatable by the user to select either a steam ironing mode of operation or a dry ironing mode of operation.
In the case of a steam iron which also has a steam surge generating capability, a momentary surge of steam can be ejected through apertures formed in the soleplate of the iron, onto the material which is being ironed, in order to flatten out wrinkles in the material, when such wrinkles are excessively difficult to remove by the normal steam ironing mode of operation.
A prior art example of a steam iron having a steam surge generating capability is disclosed in Japanese Pat. No. 48-36719, and another example in U.S. Pat. No. 4,107,860. According to these patents, the steam iron is provided with a pump mechanism which is separate from the nozzle leading into the steam generating chamber as mentioned above, i.e. the nozzle which is also incorporated in a conventional type of steam iron. Separate external operating members are provided, which are actuatable by the user for controlling the operation of the pump mechanism and the opening and closing of the nozzle, respectively, i.e. at least two separate operating members are employed for selecting the steam and dry ironing modes of operation and for generating a surge of steam when desired. These two external operating members are mounted at the forward end of the handle of the steam iron. Thus with such a prior art type of steam iron it is necessary to provide at least three external operating members, i.e. one member for enabling selection of steam ironing and dry ironing modes of operation, one member for producing a momentary surge of steam when required, and one member for the user to adjust the temperature of the soleplate of the iron to a desired value. This necessity to provide a number of separate operating members renders it difficult for the user to operate the iron, and also, due to the concentration of these operating members (i.e. push-buttons, knobs, etc) at one end of the handle of the iron, the design and manufacture of such a steam iron are difficult, e.g. because of the limited amount of space which is available at the front end of the handle of the iron.
In addition, in recent years, a new type of steam iron has been proposed, in which the water tank is removably mounted on the front end of the main body of the steam iron, in order to facilitate filling and emptying of the water tank. Such a steam iron is disclosed, for example, in Japanese Pat. No. 53-24497. This feature is extremely convenient for the user. However if such a feature were to be incorporated into a prior art type of steam iron having a steam surge generating capability, then the construction and manufacture would be extremely difficult, due to the various operating members which must be accommodated at the front end ofthe handle of the iron.
In order to overcome these problems, a configuration for a steam iron has been proposed whereby a single operating member, i.e. an operating pushbutton, is utilized both for selecting steam ironing and dry ironing modes of operation and also for generating a momentary surge of steam. An example of such a steam iron is disclosed in U.S. Pat. No. 2,782,537, and also in U.S. Pat. Nos. 3,165,843 and 3,986,282, in which a steam iron has a pump mechanism formed integrally with a nozzle which communicates with the steam generating chamber. However in the case of the steam iron of U.S. Pat. No. 2,782,537, the described construction is not suitable for practical manufacture. This is because the operating pushbutton for the pump mechanism is mounted at the rear end of the steam iron, and so it would be difficult for a user to actuate this pushbutton to generate a momentary sure of steam while moving the iron across the material being pressed. In addition, due to the fact that separate means are provided to constitute a reverse flow prevention valve for the latter pump mechanism, and to constitute means to implement changeover between dry ironing and steam ironing modes of operation, the mechanical configuration of such a steam iron is complex. Furthermore, due to the fact that the pump mechanism is disposed in the interior of the water tank, with the water intake aperture of the pump mechanism being higher than the base of the water tank, it is not possible to completely utilize all of the water contained in the water tank.
In the case of the steam iron disclosed in U.S. Pat. Nos. 3,165,843 and 3,986,282, a piston which is mounted for reciprocating movement within a cylinder of a pump mechanism also performs reciprocating movement within a water supply nozzle which supplies water to the steam generating chamber. Due to the fact that this nozzle is disposed at the base of the water tank and that the nozzle communicates directly with the cylinder of the pump mechanism, it is not possible to supply a large amount of water to the steam generating chamber by a single actuation of an operating pushbutton which is coupled to the piston of the pump mechanism. That is to say, only a limited volume of steam can be generated by a surge operation resulting from a single actuation of the latter operating pushbutton.
It can thus be understood that prior art types of steam iron designed to permit a surge of steam to be ejected momentarily when desired, present various serious disadvantages. In addition to these, the momentary supply of a surge of water into the steam generating chamber in order to produce a surge of steam will result in a sudden lowering of the temperature within the steam generating chamber, so that it is necessary to wait thereafter until this temperature has reached a sufficiently high value before generation of another surge of steam is initiated. In view of this, it has been proposed in the prior art to employ a temperature-sensitive cut-off unit in a conventional type of steam iron (i.e. a steam iron which does not include a steam surge generating capability) which will act to block the nozzle leading to the steam generating chamber, and thereby halt the supply of water to the steam generating chamber, when the temperature therein is not sufficiently high to result in instant generation of steam. Examples of such a steam iron are disclosed in Japanese Pat. No. 42-15590 and in U.S. Pat. No. 4,125,953. In the steam irons of these patents, one end of a bimetallic strip is attached to the solepate of the steam iron, and this bimetallic strip acts to open the nozzle (for supplying water to the steam generating chamber) when the temperature within the steam generating chamber is sufficiently high for generation of steam, and otherwise holds the nozzle in a closed condition. Such a temperature-sensitive cut-off device acts to limit the emission of steam in a manner tending to result in stable steam generation. However, it is even more desirable to employ such a temperature-sensitive cut-off unit in a steam iron which is capable of generating momentary surges of steam, with the amount of steam generated during each a surge being manually controllable by the user, since the momentary admission of a relatively large volume of water into the steam generating chamber in order to generate such a surge of steam will result in a temporary rapid drop in the temperature of the steam generating chamber. Thus, if no means are provided for blocking the further supply of water to the steam generating chamber in such a condition, further attempts by the user to generate a surge of steam will result only in hot water being ejected from the steam generating chamber through the apertures in the soleplate of the iron, thereby resulting in excessive dampening of the material being ironed.